This application is the national phase of international application PCT/EP97/07227 filed Dec. 22, 1997 which designated the U.S.
The present invention relates to a device for cathode sputtering for producing coatings on a substrate by means of a sputtering cathode, which can be introduced into a vacuum chamber and comprises pole shoes, a target, at least one magnet, wherein in case of a circular sputtering cathode the latter is arranged concentrically with respect to the pole shoes, the target and the magnet. The shape of the sputtering cathode of the target, the pole shoes and the arrangement of the magnet can be adapted to the shape of the substrate.
A device for cathode sputtering for the static coating of disk-shaped substrates by means of a plasma in a vacuum chamber with at least one opening, which can be closed from the outside by placing a sputtering cathode on it, is already known DE 43 15 023 A1). An elastic vacuum seal ring and an annular anode are provided between the cathode and the chamber wall, which radially enclose the openings from the outside, wherein the anode has a flat contact surface on its surface facing the cathode. The known sputtering cathode consists of a disk-shaped ferromagnetic yoke and a cooling plate. A disk-shaped insulator is inserted between these two. The target to be sputtered is arranged in front of the cooling plate, while an annularly arranged magnet is inserted in a groove on the back of the cooling plate. A counter-magnetic field is generated by the annularly arranged magnet, which affects the path of the magnetic field lines. By means of this, the path of the magnetic field lines is given an approximately parallel or lens-shaped or convex form.
In contrast thereto, it is an object of the present invention to design a sputtering cathode in such a way that an optimum magnetic flow distribution is achieved.
In achieving this object, the invention starts out from the basic idea of dividing the yoke symmetrically. In case of a circular sputtering cathode, a divided yoke or a yoke formed of two parts is arranged axially symmetrically with respect to the center axis of the sputtering cathode. The divided or also stepped realization of the yoke plate allows a very simple and cost-efficient cathode design and also the use of a simple, for example an annularly arranged magnet, which can be realized, for example, as a square or rectangular magnet and not as a ring magnet, and can easily be provided between the yoke plates. Ring magnets are more complicated and thus more expensive than square or rectangular magnets.
By using magnetic coils, which can, for example, be arranged under the target or at any other place, the magnetic field in the target space can be influenced or varied purposefully, so that the plasma can be displaced radially from inside to outside. As a result, the erosion groove can be displaced radially over the target, and it is thus possible to either produce a very wide erosion groove by continuously varying the magnetic field or two erosion grooves next to each other by stepwise switching the magnetic field back and forth.
Moreover, it is advantageous that the divided yoke is provided in the area of the ring magnet and at least one part generating a varying magnetic field.
In an embodiment of the device according to the present invention it is furthermore possible that in the area of the first or second yoke plate or in the area of the outer circumference of the first or second yoke plate at least the annularly arranged magnet is provided, wherein between the target or between the back surface of the target and the yoke plate at least one first annularly arranged magnetic coil is provided.
In a further development of the invention it is advantageous that the first magnetic coil is provided in the area of the outer circumference of the target, and the second magnetic coil is provided in the area of the cooling head.
According to a preferred embodiment of the solution according to the invention, the two magnetic coils are eventually provided slightly above an upper limit or the back surface of the target.
It is of particular importance for the present invention that the two magnetic coils are arranged in the same transverse plane between the first or second yoke plates and/or the back surface of the target.
Moreover, it is advantageous that the annularly arranged magnet arranged in the area of the outer circumference of the first and/or second yoke is provided between the upper or second yoke plate and the lower or first yoke plate or between the yoke plates arranged in one plane.
Moreover, it is advantageous that the two magnetic coils and the ring magnet are arranged concentrically with the center axis of the sputtering cathode.
In this connection, it is advantageous that the ring magnet has an outer diameter which is about as large as, slightly smaller or slightly larger than the outer diameter of the first magnetic coil.
Moreover, it is advantageous that in an insulator provided between the target and at least one yoke plate and/or in the target ring chambers for receiving the magnetic coils are provided.
In a further embodiment of the device according to the invention it is also possible that the two magnetic coils have different diameters.
In a further embodiment of the invention it is advantageous that the second magnetic coil has a smaller outer diameter than the first magnetic coil.
Moreover, it is advantageous that the ring magnet has an N/S polarity directing towards the substrate.
It is also advantageous that a shielding means is provided between the two magnetic coils.
In a further embodiment of the device according to the invention it is furthermore possible that the shielding means is provided between one of the yoke plates and the target or between the yoke plates and the substrate.
Moreover, it is advantageous that the shielding means is provided between one of the yoke plates and/or the insulator and the target.
An essential, advantageous embodiment is achieved in that the two yoke plates are spaced from each other with respect to the center axis and arranged in one plane in a target space and/or outside the target space.
Moreover, it is advantageous that the distance between the two yoke plates corresponds approximately to the height and/or width of the ring magnet.
Furthermore, it is advantageous that the two yoke plates are annular plates and that their outer diameters have different sizes and/or that they are arranged in the form of a step.
In a further development of the device according to the invention it is furthermore possible that the yoke plate having a smaller outer diameter is connected with the cooling finger and/or indirectly or directly with a hollow screw, and the yoke plate having a larger outer diameter is connected indirectly or directly with the pole shoe.
In a further embodiment of the invention it is advantageous that a means generating a varying magnetic field is provided in the area of a pole shoe.
In a preferred embodiment of the solution according to the invention it is eventually possible that the current fed to the coils can be changed depending on time.
It is of particular importance for the present invention that the current fed to the coils or the current supplied to the coils can be controlled via a control curve or a preset program and that for this purpose current conductors are in an operating connection with a computer via a current divider.
In connection with the development and arrangement according to the invention, it is advantageous that the first coil is provided in the area of the outer circumference of the yoke plate having a smaller diameter and the second coil is provided in the area of the inner circumference of the second yoke plate.
Moreover, it is advantageous that the two annular coils are also arranged in a stepped manner.
To this end it is advantageous that the shielding means arranged in the target space and/or outside the target space in the area of the substrate is arranged between the two coils in the same plane as the coils.
A further advantageous embodiment of the invention comprises at least one rotatable iron core.